Identification And Characterization Of A Novel Hydroxycinnamoyl Transferase From The Physcomitrella Patens And The Regulation Of P.Patens HCT

Since the early evolution of land plants from primitive green algae, penylpropanoid-derived compounds have played an important role in defense against pathogens, UV radiation and environmental stress in plants. Phenylpropanoid-derived compounds occur in liverworts and mosses, and mainly synthesized via phenylpropanoid pathway. Although phenylpropanoid pathway in higher plant has been extensively studied, little information is available from bryophytes. The results are as follows:1、The cloning and characterization of HCT from the moss, Physcomitrella patens. Taking advantage of the available P. patens EST sequences, a HCT (PpHCT) was cloned from the gametophores of P. patens. A phylogenetic analysis revealed that PpHCT protein sequence contains about140amino acids without finding in other HCTs.2、The heterologous expression of PpHCT in E. coli showed that this enzyme can transfer p-coumaroyl, caffeoyl or feruloyl moieties from a coenzyme A-thiolester to shikimate, whereas transfers p-coumaroyl moieties from a coenzyme A-thiolester to quinate.3、Overexpression of PpHCT in Arabidopsis thaliana caused plants to accumulate higher levels of coumaroyl shikimate, caffeoyl shikimate and feruloyl shikimate, nor did overexpression of PpHCT without the particular145amino acids. These results demonstrate that PpHCT exhibited different substrate preference profile to those of higher plant HCT.4、Using luciferase reporter assay system, we found that PpMYB58and PpMYB63decreased the expression of luciferase driven by HCT promoter, whereas AtMYB58and AtMYB63increased the expression of luciferase. This has implied that MYBs regulating lignin biosynthesis have different function between moss and Arabidopsis.